1. Field of the Invention
The invention relates to a medical guide wire which introduces a cathether when inserting it into a blood vessel system to cure vascular strictures or the like.
2. Description of Prior Art
Upon implementing an arteriography, a medical guide wire has been used as a flexible line member to insure that a catheter is inserted when introducing the catheter to a blood vessel system or applying a balloon catheter to a clogged portion of the coronary artery for a treatment purpose. These are illustrated by Japanese Provisional Patent Publication Nos. 4-25024 and 4-292175.
The medical guide wire requires a great degree of flexibility and axial load resistant property (anti-buckling property) against the direction in which the guide wire is inserted, in order to smoothly advance the guide wire into a complicatedly turned blood vessel system or a bifurcated blood vessel system.
The guide wire further requires an appropriate torsional rigidity and a good maneuverability (mechanical properties) to enable an operator to manipulate the direction in which the guide wire advances into the blood vessel system since the manipulator advances a leading end of the guide wire while rotating it outside the blood vessel system.
As a basic structure, the guide wire has a very thin wire at the leading end around which a main helical spring is fit. In order to secure a good mechanical property with the guide wire, a diameter-reduced helical spring is further placed around a leading top end of the main helical spring (xe2x80x9ctapered helical spring structurexe2x80x9d) as shown by Japanese Laid-open Utility Model Application No. 59-16649 and Japanese Provisional Patent Publication No. 6-11339.
However, the guide wire hinders a good blood flow when reaching the leading end to a vascular stricture area although the mechanical property is somewhat improved.
Further, it is necessary for the manipulator to remotely manipulate a handle grip outside the blood vessel with the turning and pushing actions accompanied when advancing and indwelling the leading end to/on the vascular stricture area.
This manipulation requires a considerably high degree of experienced skills to smoothly control the guide wire remotely. In order to smoothly manipulate the guide wire, it is also indispensable to strictly consider a rupture resistant property against a strong torsional torque, the torsional rigidity, the axial load resistant property and the good maneuverability (mechanical properties).
Therefore, the present invention has made with the above drawbacks in mind, it is a main object of the invention to provide a medical guide wire which enables a manipulator to smooth manipulation with a good torsional rigidity, an axial load resistant property and a good maneuverability.
According to the present invention, there is provided a medical guide wire comprising: an elongated flexible core member, around a leading end portion of which a helical spring is loosely fit; a spiral blood stream path provided continuously between line elements of the helical spring from a middle portion to a leading top end of the helical spring; and a gap-stopper provided at a gap between a line element of the helical spring and the core member in order to introduce a blood flow into the spiral blood stream path at the gap-stopper toward the leading top end of the helical spring.
According to other aspect of the present invention, there is provided a medical guide wire comprising: an elongated flexible core member, around a leading end portion of which a helical spring is loosely fit; the helical spring having a first helical spring having a first line diameter and a second helical spring having a second line diameter smaller than the first line diameter, the first helical spring and the second helical spring being alternately placed around the core member concentrically to form a multi-wound helical spring; and a spiral blood stream path being formed on an outer surface area of a line element of the second helical spring between line elements of the first helical spring, the spiral blood stream path beginning from a middle portion to a leading top end of the helical spring.
The basic concept of the invention is to utilize the fluid characteristics of the blood streams flowing along the blood vessel system. When the medical guide wire reaches its leading end at the stricture area within the blood vessel system, an appropriate amount of the blood flow is secured and maintained by the spiral blood stream path without clogging the blood vessel.
Due to the dynamic pressure from the blood flow, a rotational force and advancing force are provided with the leading end of the medical guide wire.
The phrase xe2x80x9cthe helical spring loosely fit around the core memberxe2x80x9d includes states that the helical spring loosely fit its inner surface into an outer surface of the core member when the core member is circular in cross section, and that the helical spring circumscribes its inner surface with the outer surface of the core member when the core member is rectangular in cross section.
The phrase xe2x80x9cthe helical spring loosely fit around the core memberxe2x80x9d includes the known xe2x80x9ctapered helical spring structurexe2x80x9d in which the tapered helical spring is placed between the diameter-reduced helical spring and the diameter-increased helical spring. Further, the phrase xe2x80x9cthe helical spring loosely fit around the core memberxe2x80x9d includes the helical spring, a helical diameter of which is uniform through its entire length.
With the spiral blood stream path continuously provided between the line elements of the helical spring (or defined on the outer surface of the helical spring), an appropriate amount of blood flow can be secured and maintained within the blood vessel system when the medical guide wire inserts and indwells its leading end portion to/on the vascular stricture area. This is true when the medical guide wire exceedingly narrows the gap between the leading end portion and the vascular stricture area, or when the medical guide wire gets its leading end portion stuck in the vascular stricture area.
When the guide wire reaches its leading end portion at the vascular stricture area from the normal blood vessel area, the blood stream area around the leading end portion decreases to quicken the blood streams. The quicken blood streams run along the spiral blood stream path to induce the dynamic pressure. The dynamic pressure provides the leading end portion with the advancing force and the rotational force.
Even under the circumstances in which the advancing force and the rotational force are induced in the normal blood vessel area due to the dynamic pressure albeit slightly, the slightly induced forces are resultantly added to the advancing force and the rotational force when the medical guide wire is inserted to indwell its leading end portion to/on the vascular stricture area. This increases the movability of the leading end portion to secure a smoother manipulation, while at the same time, reducing the manipulating force transmitted to a middle portion of the medical guide wire so as to ease the strict mechanical properties required for the medical guide wire.
With the gap-stopper provided between the helical spring and the core member, the gap-stopper acts as a blood stream weir to prevent the blood streams from flowing rearward along the leading end portion of the medical guide wire. The rearward prevention insures the required amount of the blood stream and reinforces the advancing force and the rotational force with which the spiral blood stream path provides the leading end portion.
With the spiral blood stream path and the tapered leading end portion each provided with the medical guide wire, the medical guide wire advances its leading end portion into the vascular stricture area without oscillating the leading end portion approached to the vascular stricture area.
Since the medical guide wire generally provides its leading Lop end with the semi-spherical or semi-spherically shaped head plug in order to smoothly insert the leading top end into the blood vessel system, Karman vortex street appears in front of the semi-spherical head plug when the head plug is straightly subjected to the high speed blood streams. The Karman vortex street induces to oscillate the head plug, and brings the disadvantage to hinder the leading end portion from advancing into the multiple type of the vascular stricture area (eccentric type, irregular type, complicated type, oblong type or the like).
As opposed to the above structure, most of the blood flows along the spiral blood stream path prevents the Karman vortex street from being induced when the leading top end encounters the high speed blood streams. This obviates the harmful oscillation to stabilize the leading end portion, and thereby making it easier to advance the leading end portion into the vascular stricture area.
Considering the spiral blood stream path to act as a minute lead pitch of the helical spring fit into the core member, a secondary advantage is obtained that the spiral blood stream path can be used as a xe2x80x9clubrication pool groovexe2x80x9d when applying a lubrication agent on the leading end portion in order to facilitate the insertion into the blood vessel system.